Control of an automatic darkening filter

ABSTRACT

A protective automatic darkening filter (ADF) and an associated tool, such as a welding torch, are controlled by a corresponding communication unit. The invention helps to ensure that the tool is not activated before the ADF has reached its dark state. A communication channel between the communication unit and the ADF may be established using a wired or wireless medium.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. Ser. No. 12/540,837, filed Aug.13, 2009, now U.S. Pat. No. 7,810,937; which is a continuation of U.S.Ser. No. 11/247,298, filed Oct. 11, 2005, now granted as U.S. Pat. No.7,637,622, the disclosure of which is incorporated by reference in itsentirety herein.

The invention pertains to automatic darkening protective filter lensthat is capable of changing from a light state to a dark state.

BACKGROUND

Automatic darkening filters, or ADFs, are often used for applicationslike welding where protection from intense levels of incident light,such as the glare of a welding arc, is desired. A typical ADF includeselectronic control circuitry, powered by a battery, which causes thefilter to change from a light (clear or transparent) state when notsubjected to the glare of the welding arc to a dark (nearly opaque)state upon exposure to such glare. This enables a welder to perform awelding operation and also perform tasks outside the welding areawithout removing the protective shield.

Conventional ADFs include layers of liquid crystal material capable ofchanging from a light state to a dark state under control of a controlvoltage. A sensor detects the start of a welding arc and generates acorresponding control voltage which, when applied to the filter lens,causes it to change from a light state to a dark state. Because the arcis already switched on when the sensors react, the switching of the ADFhas to be very short, e.g., less than a few hundred microseconds. Thisabrupt or “hard” transition between the light state and the dark statecan be uncomfortable to the user, especially under working conditionswhere many light-to-dark transitions are experienced throughout thecourse of a typical work day.

The sensors in a conventional ADF may be adversely affected byinterference from other light sources, other welding machines, currents,or magnetic fields in the vicinity, which could cause the ADF to enterthe dark state in the absence of a welding arc. In certainapplications—such as low current tungsten inert gas (TIG) welding—theusable signal from the welding arc is relatively weak. In these cases,the detector may fail to detect the arc, resulting in failure of the ADFto enter the dark state even in the presence of a welding arc.

SUMMARY OF THE INVENTION

The invention provides a protective automatic darkening filter (ADF) andan associated tool, such as a welding torch, which ADF and tool arecontrolled by a corresponding communication unit. The invention helpsensure that the tool is not activated before the ADF has reached itsdark state. A communication channel between the communication unit andthe ADF may be established using a wired or wireless medium.

In one embodiment, the invention is directed to a system comprising aswitchable filter that changes from a light state to a dark state inresponse to a dark state command message, a power controller thatprovides power to a tool in response to an activate tool command, and acommunication unit that generates the dark state command in response toa tool activation signal, wherein the switchable filter furthergenerates a dark state acknowledge message upon entering the dark state,and wherein the communication unit further generates the activate toolcommand in response to the dark state acknowledge message.

In another embodiment, the invention is directed to a method thatcomprises: receiving a tool activation signal; generating a dark statecommand message for a switchable filter in response to the toolactivation signal; receiving a dark state acknowledge message from theswitchable filter; and generating an activate tool command in responseto the dark state acknowledge message.

In another embodiment, the invention is directed to a method thatcomprises: receiving a tool activation signal; generating a dark statecommand message for a switchable filter in response to the toolactivation signal; waiting for a dark state wait time to elapse; andgenerating an activate tool command after the dark state wait time haselapsed.

As used in this application, the term “automatic darkening filter” (ADF)means a protective device including circuitry and a switchable filter orlens that is designed to protect a user's eyes from excessive glare inan environment such as welding or in other environments where there isthe potential for damage to the human eye from excessively bright light.The terms “switchable filter” and “ADF lens” mean a filter that iscapable of changing from a light state to a dark state in response to acontrol signal.

The details of one or more embodiments of the invention are set forth inthe accompanying drawings and the description below. Other features,objects, and advantages of the invention will be apparent from thedescription and drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a welding helmet 10 that includes anautomatic darkening filter (ADF) 14 that has a switchable filter lens 20in accordance with the present invention.

FIG. 2 is a block diagram of an ADF system in which an ADF 14 and anassociated tool 50 are controlled by a corresponding communication unit40 in accordance with the present invention.

FIGS. 3A and 3B are flowcharts illustrating unidirectional control of anADF in accordance with the present invention.

FIGS. 4A and 4B are flowcharts illustrating bidirectional control of anADF entering the dark state in accordance with the present invention.

FIGS. 5A and 5B are flowcharts illustrating bidirectional control of anADF entering the light state in accordance with the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 shows an example of a welding helmet 10 that includes a helmetbody or shell 12 and an automatic darkening filter (ADF) 14.Specifically, the ADF 14 includes an auto-darkening filter lens 20supported in the helmet shell 12. The auto-darkening filter lens 20 maybe mounted in the helmet shell 12 so that it is directly in front of thewearer's eyes when the helmet is worn by the user. In one embodiment,the switchable lens 20 is replaceable. The lens 20 may include arectangular (or other shaped) frame or housing. Examples of such filtersare described in U.S. Pat. Nos. 6,097,451 and 5,825,441, both to Hörnelland Palmer. Examples of helmet shells may be seen, for example, in U.S.Pat. Nos. 6,185,739, 5,533,206, 5,191,468, 5,140,707, 4,875,235, and4,853,973. The helmet 12 also may have clean air supplied to theinterior, and thus may include a face seal to separate a breathing zonefrom the ambient air. An example of such a face seal is shown in U.S.patent application Ser. Nos. 10/987,512, 10/987,641, 10/988,789,29/217,155, 29/217,153, 29/217,154, 29/217,107, and 29/217,156.

FIG. 2 illustrates a block diagram of an ADF system that includes an ADF14, a tool 50, a power controller 30, and a communication unit 40. TheADF 14 includes a switchable filter lens 20 that is capable of changingfrom a light state to a dark state. Control of switchable filter lens 20is provided by filter control electronics 22 via connection 24. In oneembodiment, switchable filter lens 20 may be a laminate of severaldifferent layers including, for example, UV/IR filters, polarizers, andliquid crystal elements. In other embodiments, switchable filter lens 20may be constructed using electro chrominance filters. Switchable filterlens 20 acts as a shutter that darkens in response to a control signalto shade the lens and thereby protect the user's eyes from harmful glareresulting from operation of tool 50, such as the glare of a welding arcproduced from operation of a welding torch. Examples of suitableswitchable filters are described in U.S. Pat. Nos. 6,097,451 and5,825,441, and in copending and commonly assigned U.S. patentapplication Ser. No. 11/076,081 to Magnusson et al., filed Mar. 9, 2005.

Tool 50 may include, for example, a welding torch or other type ofmachine tool or power tool. Tool 50 may be any kind of power or machinetool of the types used in many different industries—for example,carpentry tools, plumbing tools, or machine tools of other trades—and itshall be understood that the invention is not limited in this respect.For purposes of illustration, however, the invention is described as itapplies to tools used in the welding industry, such as welding torches.Power controller 30 contains the necessary power control electronicsnecessary to provide energy to tool 50.

The invention provides a protocol between the ADF 14 and a communicationunit 40 to ensure that tool 50 is not activated until the ADF 14 hasentered the dark state. A communication channel 32, which may be eitherunidirectional or bidirectional, provides for communication between theADF 14 and the communication unit 40. FIG. 2 shows the communicationchannel 32 as a wireless communication channel, although thecommunication channel 32 may also be provided via a wired connection.Wireless communication may be provided using any of the many knownwireless communication methods, such as infra-red communication, radiofrequency (RF) communication, or acoustical communication, or by anysuitable later-developed technology. Command lines 42, 44, and 46 allowcommunication between communication unit 40, power controller 30, andtool 50.

Messages that are transmitted between communication unit 40 and the ADF14 are used to control the transition of lens 20 from the light state tothe dark state and vice versa. These messages also control activation oftool 50. In this way, the system ensures that lens 20 is in the darkstate before it allows activation of tool 50. In a welding environment,for example, in which tool 50 would be a welding torch, communicationunit 40 ensures that the lens 20 is in the dark state before powercontroller 30 is allowed to ignite the welding arc. Althoughcommunication unit 40 is shown as a separate component in FIG. 2, thefunctionality of the communication unit also may be located within tool50, between a cable connecting tool 50 with power controller 30, withinpower controller 30, or other suitable position depending upon theparticular application and environment in which the system is to beused.

In addition to state change commands from communication unit 40 andstate acknowledges from ADF 14, the messages transmitted between the ADF14 and the tool controller 60 through the communication channel 32 mayalso include other information. For example, the system may ensure thateach ADF is associated with one and only one tool via unique identitycodes embedded within the messages transmitted in the communicationchannel 32. To this end, each ADF 20 may be uniquely associated with onetool 50 via at least one unique identity code transmitted in the darkstate command message. A unique association between ADF 20 and tool 50and/or communication unit 40 may help ensure that interference fromother sources of light, currents, or magnetic fields will not effect theoperation of the ADF, causing it to darken or lighten inappropriately.

The tool 50 can include at least one switch 52 through which a usercontrols the start and stop of tool 50. In a welding environment, forexample, a welder controls the start and stop of the welding arc bypressing or releasing one or more switch(es) located on the weldingtorch. Switch 52 may include, for example, push buttons, a trigger,other user actuated switch, or some combination thereof.

Actuation of switch 52, either activating or deactivating (e.g.,pressing or releasing) produces a resulting tool activation signal. Asused in this description, the term “tool activation signal” refers toany actuation of switch 52, whether to activate the tool, deactivate thetool, or adjust the amount of power applied (e.g., to adjust the speed,torque, or intensity of the tool) of the tool.

The tool activation signals resulting from actuation of switches 52 arereceived by communication unit 40 via connection 46. In response to thetool activation signals, the communication unit 40 may communicate withthe ADF 14 via communication channel 32 to ensure that the ADF lens ischanged to the proper state and then allow power controller 30 to actaccordingly. In this way, the ADF system ensures that tool 50 is notactivated before ADF 20 has entered its dark state and that the user'seyes will not go unprotected.

The system may also result in improved reliability in certainsituations. For example, each ADF may be associated with a particulartool controller via unique identity codes embedded in the messagestransmitted via communication channel 32. This configuration ensuresthat other welding machines in the neighborhood cannot influence theoperation of a particular ADF. Interference from other light sources,currents, or magnetic fields will not affect the ADF operation. Inaddition, detection of low current TIG welding can be more reliable whenthe system utilizes a command message rather than a weak photodiodesignal to detect the start of a welding arc.

FIGS. 3A and 3B are flowcharts illustrating unidirectional control of anADF. These charts are described with the identifying numerals in thefigures for the process steps being presented in parentheses. Theidentifying numerals used in the text that are not in parenthesis referto structural parts shown in FIGS. 1 and 2. FIGS. 3A and 3B show boththe process carried out by communication unit 40 for controlling thetransition from the light state to the dark state (100) and the processcarried out by communication unit 40 for controlling the transition fromthe dark state to the light state (120). Control of the transition fromthe light state to the dark state (100) begins when communication unit40 receives a tool activation signal from tool 50 (102). The toolactivation signal may be user generated by, for example, actuation ofone of switches 52 located on tool 50. In response to the toolactivation signal, communication unit 40 generates a dark state commandmessage (104). The dark state command message may include, for example,a command instructing the ADF to enter the dark state as well as uniqueidentity code(s) identifying the communication unit 40 and theassociated ADF 20 to which the dark state command is directed.

After generating the dark state command message, communication unit 40waits a predetermined length of time sufficient to allow the ADF lens 20to enter the dark state (the dark state wait time) (106). The dark statewait time may be less than 1 second, and further may be anywhere between1 millisecond and 900 milliseconds, for example. After the dark statewait time has elapsed, communication unit 40 transmits an activate toolcommand to power controller 30 (108). In one embodiment, communicationunit 40 may repeat the dark state command message one or more timesduring the dark state wait time. If the first dark state command messagewas not received correctly, the lens 20 will have another chance toproperly receive and respond to the command when the dark state commandmessage is retransmitted. Each retransmission during the wait willincrease the probability for a successful message receipt.

Transition control from the dark state to the light state (120) beginswhen communication unit 40 receives a tool deactivation signal from tool50 (122). This tool deactivation signal may be user generated by, forexample, actuation (pressing a pushbutton, releasing a pushbutton ortrigger, etc.) of one of switches 52 located on tool 50. In response tothe tool deactivation signal, communication unit 40 transmits adeactivate tool command to power controller 30 (124).

After transmitting the deactivate tool command, communication unit 40waits a predetermined length of time sufficient to allow powercontroller 30 to deactivate tool 50 (the deactivate tool wait time)(126). The deactivate tool wait time typically is less than 1 second,and may be anywhere between 1 millisecond and 900 milliseconds, forexample. After the deactivate tool wait time has elapsed, communicationunit 40 generates and transmits a light state command message to the ADF14 (128). Again, the light state command message may include a commandinstructing the ADF to enter the light state as well as a uniqueidentity code(s) identifying the communication unit and the associatedlens 20 to which the light state command is directed. The light statecommand causes the ADF lens 20 to transition from the dark state to thelight state.

FIGS. 4A and 4B are flowcharts illustrating bidirectional control of anADF lens as it transitions from the light state to the dark state. FIG.4A shows a process (150) followed by communication unit 40 and FIG. 4Bshows a process (160) followed by ADF 20 during a bidirectionalhandshaking protocol. In response to receipt of a tool activation signal(152), the communication unit 40 generates and transmits a dark statecommand message via communication channel 32 (154). Communication unit40 waits to receive a dark state acknowledge message (156) from the ADF14 via communication channel 32, indicating that the ADF lens 20 hascompleted the transition from the light state to the dark state. Inresponse to the dark state acknowledge message from the ADF 14, thecommunication unit 40 transmits an activate tool command to powercontroller 30, thus causing power to be applied to tool 50.

On the ADF 14 side of the protocol (160), upon receipt of the dark statecommand message (162), the filter controller 22 applies a correspondingcontrol voltage to switchable filter 26, causing it to enter the darkstate (164). Once the lens 20 completes its transition to the darkstate, the lens 20 transmits the dark state acknowledge message viacommunication channel 32 (166). As described above, the dark statecommand message and the dark state acknowledge message may includeunique identity code(s) uniquely associating lens 20 and communicationunit 40 as well as the dark state command and dark state acknowledge.

FIGS. 5A and 5B are flowcharts illustrating bidirectional control of thetransition of an ADF 14 from the dark state to the light state. FIG. 5Ashows a process (170) followed by communication unit 40 and FIG. 5Bshows a process (180) followed by ADF 14 during a bidirectionalhandshaking protocol. In response to receipt of a tool deactivationsignal (172), communication unit 40 generates a deactivate tool commandto power controller 30 (174). Communication unit 40 then waits untiltool 50 has been deactivated (176) indicating that power has beenremoved from tool 50. When the tool has been deactivated (176),communication unit 40 generates and transmits a light state commandmessage via communication channel 32 (178). On the ADF 14 side of theprotocol (180), upon receipt of the light state command message (182)filter controller 22 applies an appropriate control voltage toswitchable filter 26, causing it to transition to the light state (184).

In this manner, ADF 14 and communication unit 40 cooperate to ensurethat tool 50 is not activated before the ADF lens 20 has entered thedark state. Because the ADF and the communication may be uniquelyassociated with one another via unique identity codes, the invention mayhelp ensure that the operation of the ADF is not influenced by othertools in the vicinity, or by interference from other sources of light,currents, or magnetic fields.

The ADF system described herein may result in improved reliability andrelaxed requirements on the switching time of the ADF 14. For example,the ADF lens 20 may enter the dark state more slowly. Because the toolis not activated until a dark state is achieved, activation of the toolmay be delayed for an arbitrary length of time (generally some number ofmilliseconds, such as anywhere between 1 millisecond and 900milliseconds) allowing enough time for the lens to go completely dark.This means that a “soft” change from light to dark state may beutilized. A smooth transition from light to dark state is morecomfortable for the user's eyes than an abrupt change. Also, slowertechnologies, such as electro chrominance technology, may be used forthe switchable filter. Advantages offered by electro chrominancetechnology may include a “lighter” light state, the potential for betteroptical characteristics, and lower cost.

The invention may also help to ensure that the ADF is not adverselyaffected by interference from other sources of light, other weldingmachines in the vicinity, currents, or magnetic fields that could causethe ADF to enter the dark state even in the absence of a welding arc.Further, the transition to the dark state does not rely on sensing of awelding arc or other source of incident light from which the user is tobe protected. Thus, the danger of failing to enter the dark state inthose applications where the welding arc signal is weak is reduced oreliminated. Thus, the invention helps to ensure that the ADF providesproper protection to a user in a wide variety of situations andenvironments.

All of the patents and patent applications cited above, including thosecited in the Background Section, are incorporated by reference into thisdocument in there respective entireties.

Various embodiments of the invention have been described. For example, asystem comprising an ADF and associated tool have been described ensurethat the tool is not activated before the ADF has reached its darkstate. Nevertheless, various modifications may be made to the systemdescribed herein without departing from the spirit and scope of theinvention. For example, although primarily described in the context ofwelding, the invention may have broad application for a wide variety ofother systems or fields. These and other embodiments are within thescope of the following claims.

1. A system, comprising: a switchable filter, comprising an electrochrominance filter; a communication unit; and a power controller;wherein the switchable filter changes from a light state to a dark stateafter receiving a dark state command message from the communicationunit, and changes from the dark state to the light state after receivinga light state command message from the communication unit; and whereinthe communication unit repeatedly generates and transmits the dark statecommand message to the switchable filter during a predetermined lengthof time and after receiving a tool activation signal, waits thepredetermined length of time sufficient to allow the switchable filterto enter the dark state after generating the first dark state commandmessage, and generates and transmits an activate tool command after thepredetermined length of time has elapsed, generates and transmits adeactivate tool command in response to a tool deactivation signal, waitsfor a predetermined deactivate tool wait time to elapse and generatesthe light state command message; and wherein the power controlleractivates a welding tool after receiving the activate tool command anddeactivates the tool after receiving the deactivate tool command.
 2. Thesystem of claim 1, wherein the predetermined length of time is between 1millisecond and 900 milliseconds.
 3. The system of claim 1, wherein thecommunication unit transmits the dark state command message via awireless communication channel.
 4. The system of claim 1, wherein theswitchable filter is positioned within a safety helmet.
 5. The system ofclaim 1, wherein at least one of the dark state command message and thelight state command message includes a unique identity code.
 6. Thesystem of claim 1, wherein the communication unit and the switchablefilter are associated with one another via unique identity codes.
 7. Thesystem of claim 1, wherein the tool is activated 1 to 100 millisecondsafter the switchable filter has entered the dark state.
 8. A system,comprising: a switchable filter, comprising an electro chrominancefilter; a communication unit; and a power controller; wherein theswitchable filter changes from a light state to a dark state afterreceiving a dark state command message from the communication unit, andchanges from the dark state to the light state after receiving a lightstate command message from the communication unit; and wherein thecommunication unit generates and transmits the dark state commandmessage to the switchable filter after receiving a tool activationsignal, waits a predetermined length of time sufficient to allow theswitchable filter to enter the dark state, and generates and transmitsan activate tool command after the predetermined length of time haselapsed, generates and transmits a deactivate tool command in responseto a tool deactivation signal, waits for a deactivate tool wait time toelapse and generates the light state command message; wherein the powercontroller activates a welding tool after receiving the activate toolcommand and deactivates the tool after receiving the deactivate toolcommand; and wherein the switchable filter generates and transmits adark state acknowledge to the communication unit upon entering the darkstate.